Is it a preamplifier, a DAC, a Bluetooth receiver or a headphone amp? It’s all of them! The initial pictures of the HA-1 on Oppo’s website (and in print) displayed it with a spectrum analyzer giving the piece the look of an ‘80s equalizer. Well, the good news is that the HA-1 is really a fully functional headphone amplifier. And, as an aside, the front panel display is adjustable so the unit can show simple operational information or cool-looking retro VU meters. (I noticed Oppo is advertising the HA-1 in Stereophile with the VU meters instead of the spectrum analyzer. Someone must have clued them in…)

Aside from some subjective adjustments like the display, brightness level, etc. the user should try the gain adjustment to determine which will work best with the headphones being used. I found with a set of Audeze LCD-X ‘phones that the high setting sounded better. A fellow audiophile commented on how dull things sounded with the low setting (with another set of headphones).

A few miscellaneous notes: First, the unit runs very hot. You definitely don’t want to block the vented area on top although even the top surface runs rather hot, so I would avoid putting anything directly on the amp. If you are a stickler for “authenticity” you will notice the meters do not react like analog meters—they are too slow to match the movement of typical meters and a bit jerky, so they don’t match a “slow response” mode either. Every input switches via a loud “click” (relay) and takes about 5 seconds to switch.

USB. I ran the output of my office desktop computer (running Win7 and using Foobar2000) into the Oppo. I had to install a driver that is readily available on the Support page for the HA-1 on Oppo’s website. Once the driver was installed I went into the Control Panel and made sure the sound output was set to the Oppo. I also checked the settings and adjusted up to 192/24 bit and made sure the signal working into the amp (with the “test” button in the sound properties control panel). Additionally, you will want to click on Oppo’s Control Panel (on the computer—not on the unit). According to the software the Asio buffer sample size was too small, so I increased it.

All the music (and sounds) worked well through the amp. I found the large volume control a nice way to quickly and easily get the variable YouTube videos sound under control. It turned out to be a nice addition to my desktop at work.

iPhone App. The control app worked via Bluetooth. Playback controls actually worked with Foobar without any additional work on my part. I was able to sit on the couch and (with from within the app) advance through the playlist or pause. Volume steps were in .5dB adjustments and all the controls worked smoothly.

Remote Control. The small remote that comes with the Oppo is metal and has excellent off-access response. It worked just as well as the iPhone control app, so if you are “old school” then it should serve you well. You could always program the IR functions into a learning remote control for operation too. When the iPod was connected the remote’s skip and pause functions worked as expected, so you won’t have to put hands on the phone/iPod once it has been started.

Balanced vs. Unbalanced Headphone Output. Audeze is one of the only manufacturers I’ve seen that includes the necessary cable to connect to the balanced headphone output on the front of the amp. I was curious to hear how much difference there is with this connection.

First of all, the connection does not lock into place like XLR connections. Also, I should mention that while the standard ¼” jack is plugged in then this one will not operate—so it is not possible to use two sets of headphones with this unit (simultaneously). There is a dramatic difference in level (~ 10dB) between these connections, so I had to do my best to adjust for this. The plug requires some care as it goes in only one way (like a computer PS/2 connection). I think the balanced connection offered a slightly better sound, but it was close enough that I wouldn’t make this part of a buying decision.

DAC. To test the DAC I hooked up a NAD Bluesound Node. This piece is a $450 hi-res streaming box with both optical and analog outputs. I connected both so I could easily switch between the internal DAC of the HA-1 and the DAC inside the NAD. The optical connection was noticeably better, so I did the majority of the comparisons using it. With the myriad connections to the Oppo it’s easy to see which offers the best performance from every device.

iPod. It is more common today to see USB inputs designed to connect directly to the iPod. This is a different (Type A) plug from the Type B plug that is on the back (for connection to a computer). If you have the charging cable that came with the phone/iPod, this is how you’d get it connected. There are also upgraded cable options available (not tested). As mentioned earlier, I controlled the iPod with one of the remote options. This option worked well and eliminates the need for a separate iPod dock.

Bluetooth. I tested music from my iPhone 4S and the distance was extremely impressive. I was able to get over 30’ away with a couple walls in between and the Bluetooth did not cut out. I’m not sure how often the listener would be this far away as you would normally be in range of a headphone cord. In any case, the sound quality was good and range was excellent.

Stereo Preamplifier. I briefly tried the HA-1 as a stereo preamplifier even though most users will probably never use this functionality. There was a distinctive buzz when the amplifier was turned on, but the Oppo piece was off. It is usually recommended to turn the amplifier on last when starting a listening session and the amplifier off first when shutting down. If this were the case, then I would never have noticed this condition. Not sure why it occurred. As for the sound, it was fine and would be competitive, if not more feature-rich, in comparison to other products in this price range.

Amp Comparison. Because everyone loves a good comparison I thought I’d try a less expensive Music Hall ph25.2 ($400). I ran the signal analog from a Marantz CD5005 (also $400). For kicks I first compared the headphone output from the Marantz with the Music Hall. There was more richness to the sound with the ph25.2, but I was surprised at how good the CD player was. With a modest pair of headphones this would be sufficient (assuming of course you were only listening to CDs). I picked a couple of tracks and went back and forth between the Oppo and the Music Hall. Compared to the Oppo the ph25.2 was thicker and richer, but the Oppo was cleaner and had more resolution with both voice and instrumentation. Some of the finesse, ease and smoothness on the top end was missing with the ph25.2. All in all, the Oppo was better sounding with both good and bad recordings. Without a high-end set of headphones the differences might not have been as noticeable.

I spent days listening to audiophile favorites like Norah Jones, Steely Dan and Jazz at the Pawnshop as well as “normal” music with questionable production value. I always found the sound from the HA-1 highly listenable. The Oppo comes packed with features (like DSD support!) and connectivity options, so it’s unlikely that you’ll find a standard audio component (or portable piece) that can’t get sound into it. These days headphone amps are becoming a more popular category and Oppo’s HA-1 is a nice addition to their line (to match with headphones they offer as well). If you need a full-featured, all-in-one headphone amp, then look no further!